1. Field
The present application relates generally to wireless communications, and more specifically to techniques for optimizing the timing of multi-mode system scans.
2. Background
Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal communicates with one or more base stations via transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. This communication link may be established via a single-in-single-out, multiple-in-signal-out or a multiple-in-multiple-out (MIMO) system.
With the deployment of a multitude of wireless technologies worldwide and support for these technologies in mobile multimode devices or entities, there is a growing need for seamless system selection toward the goal of global roaming. Furthermore, any particular geographic region may support mixed technologies and networks, such as 3rd Generation Partnership Project (3GPP) and 3rd Generation Partnership Project 2 (3GPP2) technologies.
A mobile multimode device that supports mixed technologies may include multiple databases that are used in selecting optimal networks within a technology. As an example, for 3GPP2 technologies, such as certain Code Division Multiple Access 2000 (cdma2000 or C2K) networks, a Preferred Roaming List (PRL) database which is stored at the UE provides information about which system/network from 3GPP2 technologies is preferred in a geographic region for that device. Whether predetermined or programmed via Over-The-Air (OTA) management protocols, the PRL contains information about the preferred networks and the order in which they should be selected for the user. PRLs for 3GPP2 technologies may be structured to have a table associated with each geographical region, which in turn contains a list of system descriptions keyed by System Identifier/Network Identifier (SID/NID) pairs and associated with an acquisition index. The acquisition index may be used as a pointer to an acquisition table which contains an indexed list of RF channels for channel acquisition purposes in the related system.
On the other hand for 3GPP technologies, such as Global System for Mobile (GSM) and Universal Mobile Telecommunication System (UMTS) Terrestrial Radio Access (UTRA), a differently structured database list of preferred networks, termed Public Land Mobile Networks (PLMNs), is stored in a Subscriber Identity Module (SIM) or Universal Subscriber Identity Module (USIM) of the mobile device. The PLMNs in the database include a Mobile Network Code (MNC) that is used in combination with a Mobile Country Code (MCC) (also known as a “MCC/MNC tuple”) to uniquely identify a service operator using a 3GPP technology, such as GSM and UMTS public land mobile networks.
The starting point can be the 3GPP approach to system selection based on PLMN lists, which may include 3GPP2 access technology identifiers (ATI), also known as Radio Access Technologies (RATs). A PLMN may identify and may be a concatenation of a MCC and a MNC. When roaming through geographical locations, it is desirable that a multimode device seamlessly select the best available system, particularly when roaming across areas with different available access technologies (e.g., 3GPP and 3GPP2). Accordingly, there is a need to manage access technology selection for multimode roaming between existing access technologies, as well as possible future access technologies, for seamless and efficient system selection among the access technologies. In particular, there is a need to intelligently manage the timing of preferred system scans in order to achieve a balance between minimizing the acquisition time and minimizing the power spent in performing such scans.